In recent years, since the quality of electric energy is capable of causing substantial economical impacts on industrial users, the issues concerning the quality of electric energy have attracted more and more attention, and the voltage disturbances at the power supply side, such as temporary-drop, surge, imbalance, etc. are considered as the most destructive ones among various problems of the quality of electric energy. Along with the increased use of power sensitive electric equipment in control processes and in automation processes, the voltage disturbances have caused destruction to industrial processes and have brought about substantial economic losses to users. Because it is necessary to further reduce voltage disturbances, great attention has been paid to finding a method for detecting and recording voltage disturbance waveform.
Currently, various types of electric energy detection equipment such as power monitoring devices (PMD) and advanced electric meters, etc. are broadly used in industry. In recent years, as the attention to the voltage disturbance has increased, users have made a demand on electric energy detection equipment: that is, it is desirable for it to have the capability of effectively detecting the voltage disturbance, furthermore, it is desirable to have the function of waveform capture so as to aid the users to analyze easily the root causes of the voltage disturbance and to make a corresponding strategy for controlling them. In view of the limited internal resources of electric energy detection equipment, especially of a PMD, the detection response time needs to be comparatively fast, while the response time of an existing detection methods based on voltage virtual value is slow, therefore, it is desirable to propose a new method which is capable of meeting the aforementioned requirements and to be realized easily in electric energy detection equipment.